Systems and methods for limiting the power output of an engine, for fuel economy and other purposes are well known in the art. For example, U.S. Pat. No. 6,052,644, issued to Murakami et al. on Apr. 18, 2000 teaches an device and a method for limiting the vehicle speed in which the apparatus judges a vehicle speed limit traveling period when a vehicle speed signal is equal to or greater than a vehicle speed limit value, to calculate a corrected depressing stroke signal by a control gain based on a deviation value between the vehicle speed signal and the vehicle speed limit value so that the deviation value becomes smaller to output to an engine control device, and judges an accelerated traveling period, when the vehicle speed signal is smaller than the vehicle speed limit value and the corrected depressing stroke signal is larger than a depressing stroke signal, to output the depressing stroke signal to the engine control device. However, disadvantageously, such devices as that disclosed by Murakami only regulates the speed of the vehicle by taking into account the actual speed of the vehicle and correcting the speed of the motor only after the speed of the vehicle has surpassed or fallen below the vehicle speed limit value, and are thus not ideal for purposes of economizing fuel. Further, such devices do not take into account the mass of a load carried by the vehicle.
Japanese patent application publication number 05221251, filed on Feb. 12, 2002 by Komatsu Ltd. with Hattori Masaharu named as inventor, discloses another device for limiting the output of an engine, and thereby the speed, of a dump truck which obviates some of these disadvantages by taking into account the mass of a load carried by the dump truck using a pressure sensor. However, the system taught by Komatsu is above all conceived for preventing overloading of the dump truck and damage to a surface upon which the dump truck operates. Further, the device taught by Komatsu is complicated in that it requires connection to a multiplicity of components, including a transmission shifting device, rotational speed sensors for the motor, and to a pressure sensor.
Accordingly, an improved fuel economy system and method for a vehicle is required.